渤海海峡北部沿岸流季节变化特征

本文基于渤海海峡北部沿岸一观测站点长时间序列海流观测数据分析了海峡北部沿岸流的季节变化特征。冬夏两季余流平均流速均呈现表层最大，中层最小，底层较中层略微增大的分布态势。冬夏底层余流均存在跨等深线向岸的分量，表明底层水向岸的运动是两季都存在的现象。对余流用矢量经验正交分解得到的第一模态空间分量显示，两季余流主要是沿着等深线变化的，冬季各层余流主体变化步调一致，夏季表层与其他各层变化位相相反。风应力是引起余流变化的因素之一，但并不是主要因素。交叉谱分析亦表明，冬季余流变化滞后风应力18 h，与风应力在周期为6 d的波动成分上相关性显著；夏季余流变化滞后风应力9 h，与风应力在周期为0.8 d的波动成分上相关性显著。

Seasonal variation of the coastal currents in the Northern Bohai Strait

The seasonal variation of the coastal currents in the northern Bohai Strait has been investigated using long time-series current observational data.The mean current velocities in winter and summer both showed the largest values in the surface layer and the lowest values in the middle layer.In the bottom layer, the current velocities increased slightly comparing to the middle layer.In both seasons, the currents in the bottom layer showed shoreward cross-isobathic components, which suggested the shoreward movement of the bottom water existed all the year round.The current data were then analyzed with vector Empirical Orthogonal Function.The spatial mode of EOF1 showed that in both summer and winter, the currents mainly fluctuated along the isobaths.In winter, currents of the whole vertical profile varied in phase, and in summer the currents in the surface layer varied out of phase with the currents in the other layers.Surface wind was one of the forces in generating the currents in the study area, but it was not a dominant one.In winter, the current fluctuations lagged the wind by 18 hours and the current was significantly correlated with the wind of 6 days fluctuation period.In summer, the current lagged the wind by 9 hours and current was significantly correlated with the wind of 0.8 days fluctuation period.